Weighing instruments measure the mass of an object by measuring its weight. Electromagnetic force compensation scales are scales, in which the pan rests on a shaft above parallel guides, one of which extends beyond its fixed fulcrum to an electromagnet. The electromagnet exerts a force on its end of the guide, which acts as a lever. A sensor detects when the lever is up or down, that is, when the electromagnet's effect on the lever does not yet match the effect of the object to be weighed. The sensor feeds this information back to an amplifier which adjusts the coil current. When the lever is at a given null point, a processor uses the coil current to determine the weight.
Electronic scales with an incorporated keypad are known. They include an electronic balance or scale with a weighing pan or tray, a weighing system, a display, an operating keyboard, a 10-digit numbered keyboard for the entry of any given numerical data, and a digital electronic signal processing system or processor.
Electronic balances of this kind are generally known and described, for example, in German laid-open publication DE 35 40 749 A1.
The arithmetic capabilities of known balances are very limited. Known balances are able to subtract a tare value and to multiply certain values with a factor, for example for a percentile conversion, a conversion to other units of measurement (i.e., carat or mole) or a price calculation at balances of store counters. Furthermore, there are balances with fixed application programs, e.g., for the determination of density according to the buoyancy method, for the calculation of buoyance of air, or for the calculation of drying factors. However, these balances can only use a pre-programmed formula. Therefore, they can only be utilized for the respective purpose. If further arithmetic steps should be carried out, it is therefore customary to connect the balance via a data output to an external calculator to carry out the additional arithmetic steps. However, programming knowledge is required to incorporate the measured mass from the balance into the individual arithmetic program.
Therefore, it is one object of this invention to introduce a balance in the above mentioned form, which is able to convert the measured masses according to a wide variety of formulae without requiring programming knowledge of peripheral devices.